The present invention relates to an image processing apparatus for use as a computer peripheral; more specifically, an image processing apparatus capable of performing a high speed processing using a laser beam.
Laser beam printers and the like image processing apparatus are now requested to be capable of printing large capacity image data provided by a computer with superior picture quality at a high speed. The mainstream technology used among such image processing apparatus is overlaying of image data delivered in pluralities of colors into a full-color picture.
In a conventional image processing apparatus, however, there arises during overlaying of a pluralities of image data a disjunction among respective image data, due to various reasons, in the magnification index along main scanning direction (main scanning magnification index). For example, when generating a color image by exposing image data of four colors, cyan (C), magenta (M), yellow (Y) and black (K), on a printing object one after another using a laser beam, etc., each of the laser beams for respective colors takes a different light path of its own en route to a photosensitive body. There is a subtle difference in the characteristics of the lenses for respective colors among each other, which difference results in a subtle dislocation among the colors when an image is generated on a printing object. In a practical fixed picture, such dislocation reveals itself as a chromaticity difference, or a roughness in the contour or on the image surface. If, in a conventional processing apparatus, an image is requested to be generated with a precise location alignment, all of the mechanical systems and the optical systems concerned are requested to be provided with a very high mechanical precision level. This leads to a high cost of the processing apparatus.
The present invention aims to offer an image processing apparatus, with which the occurrence of disjunction among the pluralities of image data in the main scanning magnification index is prevented at an inexpensive cost.
In printing a plurality of image data, for example, C, M, Y and K data overlaid together, difference in the main scanning magnification index among each other, or difference in the pixel counts along the main scanning direction may result in a displacement of colors among each other. An image processing apparatus in accordance with the present invention aims to prevent occurrence of the displacement during overlaying by making each main scanning magnification index identical to each other; namely, with one image data having the largest pixel counts per line and does not need to add any further pixel, or having a high main scanning magnification index, as reference, virtual data pixels are inserted into other image data to make their main scanning magnification indices even.
An image processing apparatus of the present invention comprises
an input image data connection means for connecting with an external device,
a parallel/serial converter for converting the parallel/serial conversion on input image data,
a memory for storing the converted image data,
a write control means for controlling writing of image data into the memory device,
a read control means for controlling reading of image data out of the memory device,
a setting means for storing control information specified by an external central processing unit,
a computation means for computing, in accordance with setting information of the setting means, a timing for inserting pixel data into the image data to form a certain specific pixel unit,
a position correction means for adjusting a timing of outputting the image data, and
an output image data connection means for transmitting the image data after having been inserted with the pixel data to an external device.
In an image processing apparatus of the present invention, image data are stored into memory device under the control of the write control means, while the read control means independently reads image data out of memory device. Data pixel is inserted into the image data at every specific timing computed by the computation means. In this way, a disjunction in the main scanning magnification index among a plurality of image data is prevented at an inexpensive cost, yet with a high precision level.
Another image processing apparatus in accordance with the present invention further comprises diffusion means for calculating a diffusion quantity based on information set at the setting means, and diffusion quantity writing means for writing a diffusion quantity calculated by the diffusion means into the computation means, and controls the timing for reading image data out of the memory device and inserting pixel data into the image data.
Still another image processing apparatus of the present invention further comprises diffusion frequency generating means for generating a diffusion frequency that is controllable by an external central processing unit. The diffusion frequency generation means generates an irregular timing information, and controls the timing for reading image data out of the memory device and inserting pixel data into the image data.